1. Field of the Invention
The present invention relates generally to a method and apparatus for the treatment of blood and, more specifically, to a method and an apparatus which can be used for permitting respiration support therapy on a patient.
2. Description of Related Art
Extrarenal blood purification systems or so-called “haemofiltration systems” exist which provide for purifying the patient's blood of waste liquids and/or soluble substances which accumulate in the blood for pathological and/or surgical reasons, and/or as a result of substances administered to the patient. Such haemofiltration systems thus perform the functions normally carried out by healthy kidneys in correct working condition.
Haemofiltration systems of the above-type normally include a blood purification circuit, along which the patient's blood, is fed to add any necessary supplements and/or to purify it of any toxic solutes. The blood purification circuit is connected to the patient by two feed conduits or catheters: one for supplying the non-purified venous blood of the patient to the purification circuit, and the other for feeding the purified blood into the patient's vein.
The purification circuit normally includes a pump connected to a first catheter by a conduit for receiving the patient's blood, which pumps the patient's blood along the purification circuit. The purification circuit also includes a unit for adding an anticoagulant to the blood, and a heating and supplementing unit for adding a liquid supplement to the blood and heating the liquid supplement to a predetermined temperature. The purification circuit also includes a blood purifying filter, or so-called haemofilter, which is connected to the second catheter, and provides for eliminating any toxic elements in the blood before it is fed back to the patient's body.
In certain patients in particularly critical condition, extrarenal purification therapy must very often be accompanied by respiration support therapy, by which the oxygen concentration of the patient's blood is supplemented by removing excess carbon dioxide (CO2) from the blood. Although the above-described systems provide for highly effective extrarenal blood purification, they fail to provide for simultaneous respiration support therapy. Accordingly, the above-described systems require that the patient must be ventilated by non-physiological means during extrarenal purification therapy, with obvious drawbacks and discomfort to the patient.
United States Patent Application No. 2004/0143207 describes a blood treatment apparatus which can be used in a continuous renal replacement therapy (CRRT) capable of carrying out the so called “decapneization” of blood, in other words, of removing CO2 from the blood itself. This apparatus is provided with a blood deputation circuit through which the patient's blood passes, so that any substances to be reintegrated can be purified from any toxic solutes. It is connected to the patient by means of a first catheter which conveys the blood to be depurated, which flows inside the patient's vein into the blood deputation circuit, and a second catheter which conveys the depurated blood back into the patient's vein.
The deputation circuit consists of a pump which is disposed and acts downstream of the first catheter so that it receives the patient's blood and puts it into circulation inside the deputation circuit of a unit in order to add an anticoagulant to the blood. The circuit includes a heating and reintegration unit capable of adding a suitable reintegration liquid to the blood and to bring it to a predetermined temperature. The circuit also consists of a blood depuration filter (the “haemofilter”) connected to the second catheter to eliminate the toxic elements present in the blood before it is introduced again into the patient's body. When inserted in the deputation system described above, the apparatus of United States Patent Application No. 2004/0143207 consists of a hoxygenator; in fact, for some patients whose health conditions are particularly serious, it is necessary to accompany the external renal depuration therapy with a respiratory support therapy and to remove the excessive amount of carbon dioxide from the blood itself. If the patient does not need a substitutive renal therapy, that is to say if the patient's renal functions are correct, the CRRT therapy is not necessary, and it even may be harmful.